DEM data acquisition

DEM data can be obtained in many ways, such as topographic map contour digitization, aerial photogrammetry, stereo satellite remote sensing, laser altimetry, synthetic aperture radar remote sensing (SAR) and so on. Xiangshan DEM data is obtained from 1∶50000 topographic map. The topographic maps of the 1∶50000 standard map involved in the study area are Tuoshang map, Yihuang map, Duer map and Le 'an map (see Table 2. 1). The software platform used for acquisition is MapGIS6.5, and the projection conversion parameters are as follows: the coordinate system type is geodetic coordinate system, the projection type is Gauss-Kruger (6-degree area) projection, and the ellipsoid parameters are. See figure 7. 1 for the operation flow.